The present invention relates generally to process control systems and, more particularly, to a process control configuration system that integrates the configuration and control of device networks which use a local or specialized input/output interface with the configuration and control of device networks which use a remote input/output interface, such as the Profibus interface.
Process control systems, like those used in chemical, petroleum or other processes, typically include at least one centralized process controller communicatively coupled to at least one host or operator workstation and to one or more field devices via analog and/or digital buses or other communication lines or channels. The field devices, which may be, for example, valves, valve positioners, switches, transmitters (e.g., temperature, pressure and flow rate sensors), etc. perform functions within the process such as opening or closing valves and measuring process parameters. The process controller receives signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices via an input/output (I/O) device, uses this information to implement a control routine and then generates control signals which are sent over the buses or other communication channels via the input/output device to the field devices to control the operation of the process. Information from the field devices and the controller is typically made available to one or more applications executed by the operator workstation to enable an operator to perform any desired function with respect to the process, such as viewing the current state of the process, modifying the operation of the process, configuring the process, documenting the process, etc.
In the past, conventional field devices were used to send and receive analog (e.g., 4 to 20 milliamp) signals to and from the process controller via analog lines. These 4 to 20 ma signals were typically indicative of measurements made by the device or of control signals generated by the controller required to control the operation of the device. Each of these conventional field devices was typically individually connected, via a separate line or communication channel, to a local input/output (I/O) device which, in turn, was connected directly to a controller to enable communication between the controller and the devices. These separate lines or communication channels enabled signals measured by the device to be sent individually to the controller at any time or to enable control signals to be sent individually by the controller to the device at any time. This configuration, in which the I/O device multiplexes signals delivered directly from field devices to a controller and vice-versa is called local I/O.
In the past decade or so, smart field devices including a microprocessor and a memory have become prevalent in the process control industry. In addition to performing a primary function within the process, smart field devices may store data pertaining to the device, communicate with the controller and/or other devices in a digital or combined digital and analog format, and perform secondary tasks such as self-calibration, identification, diagnostics, etc. A number of standard and open smart device communication protocols such as the HART(copyright), PROFIBUS(copyright), Actuator Sensor Interface (hereinafter xe2x80x9cAS-Interfacexe2x80x9d or xe2x80x9cASIxe2x80x9d), WORLDFIP(copyright), Device-Net(copyright), CAN, and FOUNDATION(trademark) Fieldbus (hereinafter xe2x80x9cFieldbusxe2x80x9d) protocols, and have been developed to enable smart field devices made by different manufacturers to be used together within the same process control network.
Generally speaking, for some of these specialized communication protocols such as the Fieldbus protocol, numerous devices are attached to a bus or a network and communicate with an I/O device (which is connected to the controller) over the bus or network. In the case of the Fieldbus protocol, each device is able to send one or more signals separately to the I/O device and, thereby, to the controller. As a result, the Fieldbus protocol uses a bus to perform specialized I/O because each device can communicate individual signals (having individual signal tag names, etc.) at any desired time or at particularly specified times. Similarly, the HART protocol uses a separate line or communication channel extending between each HART device and the I/O device, which enables HART signals to be sent separately to the local I/O device at any time. As a result, the HART protocol provides local I/O operations.
However, others of the smart protocols, such as the Profibus and the AS-Interface protocols, use what is commonly referred to as remote I/O because, generally speaking, the I/O device connected to the field devices is located remotely from the controller and is connected to the controller via a further I/O device. In effect, each Profibus and AS-Interface device (or groups of these devices) has an I/O unit associated therewith. This I/O unit, which is typically located on or near the device with which it is associated, receives the different signals associated with the device and then multiplexes these signals by concatenating these signals into a single data string and placing that data string onto the bus to which other Profibus or AS-Interface devices and, therefore, other Profibus or AS-Interface I/O units, are connected. The data strings from the remote I/O devices are sent over the bus and are received by a master I/O device which is typically located near the controller. The mater I/O device receives the data strings and places these data strings in a memory associated with the master I/O device. Likewise, the master I/O device sends commands and other signals to each of the remote I/O devices by concatenating a set of such signals together (i.e., all of the signals to be sent to a particular device) and then sending this concatenated data string over the remote I/O bus to the I/O units down in the field which, in turn, decode those signals and provide the decoded signals to the appropriate locations or modules of each device.
The master I/O device typically interfaces with a controller, such as a specially designed programmable logic controller (PLC), that performs process control functions. However, the controller or the PLC must know where the individual data associated with any particular signal is stored in the memory of the master I/O device to be able to receive data from a remote I/O field device. Likewise, the controller or the PLC must know where, in the master I/O device memory, to place commands and other data to be delivered to the remote I/O field devices over the remote I/O bus. Because of this requirement, the controller or PLC designer must keep track of what type of data (e.g., string, floating point, integer, etc.) is stored at each memory location within the master I/O device and what the data at each memory location within the master I/O device represents (e.g., to which signal of which remote I/O field device this data belongs). Likewise, when sending data to a remote I/O field device, the controller or PLC must be programmed to place the appropriate type of data at the appropriate memory location within the master I/O device to assure that the correct data string is sent to the designated remote I/O field device.
Most remote I/O communication protocols, such as the Profibus and AS-Interface protocols, specify only the form of the data strings to be placed on the remote I/O bus, e.g., how long the data strings can be, how many signals can be concatenated to form a single data string, the baud rate that the data strings are to be sent, etc., but do not specify or identify the type of data to be sent. Thus, while, the manufacturer of each Profibus device usually provides a GSD (a German acronym) file having some information about the device, such as the number and types of modules that can be placed in a device, the number of bits or bytes of input and output data associated with each device signal that is communicated to the device or received from the device over the Profibus bus, etc., the GSD file does not explain what the data in the string of data sent to and received from a device represents. As a result, the system configurator must keep track of what the data received at the Profibus master I/O device represents, including what signal this data represents and whether that signal is an analog, digital, floating point, integer, etc. value. Similarly, the AS-Interface devices, which send four-bit digital signals over a remote I/O bus, leave it up to the system designer to know or to understand what each of the bits being sent over the device network bus represents.
Because of the constraints placed on the process control system by the remote I/O network, prior art process control systems using remote I/O device networks required that the remote I/O device network, along with the master I/O device, be configured independently of the rest of the process control system to assure that the controller or PLC could then be configured to use the memory locations (within the master I/O device) selected or established for each of the signals associated with each of the remote I/O field devices. Thus, to configure a process control system that used remote I/O field devices in the prior art systems, the system engineer had to first set up the remote I/O device network by connecting all of the desired field devices and the remote master I/O device to the remote I/O bus. Then, using available configuration tools (provided by, for example, Siemens) run on a personal computer, such as a laptop computer, connected directly to the remote master I/O device, the configuration engineer had to enter data specifying the devices connected to the remote I/O bus. The configuration tool then configured the master I/O device and, in doing so, selected the memory locations within the master I/O device to be used for each of the signals being received from and sent to the remote I/O field devices. Thereafter, once the remote I/O device network was set up and the master I/O device was configured, the engineer had to program the controller or the PLC to get data from and send data to the appropriate memory locations within the remote master I/O device while performing a process control routine or function. This, of course, required the engineer to enter data pertaining to each of the remote I/O field devices (and the addresses of their associated signals in the master I/O device) into the controller or PLC configuration database. Next, if desired, the engineer had to provide documentation as to which remote I/O field devices were attached to the system and how the controller or PLC properly communicated with these devices via the master I/O device. This multi-step configuration process was time consuming, had to be done separate and apart from configuring the process control system to communicate with devices using specialized, local or conventional I/O and required the entry of the data related to the remote I/O devices in at least two and possibly three separate systems at two or three different times, i.e., when configuring the master I/O device, when configuring the controller or PLC to properly communicate with the master I/O device, and then when documenting the manner in which the remote I/O devices were communicatively coupled to the controller or PLC. The requirement to enter the same or similar data in multiple databases could lead to errors in the configuration or documentation.
As noted above, third party vendors now sell software and/or hardware systems that configure a Profibus master I/O device by populating a database with the necessary data to enable the master I/O device to provide communications over the Profibus network. However, to the extent these third party systems provide documentation of which signals are stored in which memory locations of the master I/O device, this documentation is limited to the devices in the Profibus network and is not capable of being used by any other network within the process control system not using the Profibus protocol without re-entry of that data in a different database.
The data coordination activities needed to keep track of and document which signals are being placed in what memory locations within the master I/O device, what physical phenomena those signals represent and how those signals are configured (i.e., what kind of data they represent) can therefore become very involved and tedious, especially when numerous devices are connected to the Profibus, AS-Interface or other remote I/O network. Furthermore, if not properly documented, this signal coordination can cause errors when reconfiguring the devices on the remote I/O device network because such reconfiguration tasks may require reprogramming of the controller or the PLC which would, necessarily, entail re-determining what each of the signals in each of the registers of the PLC or in the controller represent and how these signals are obtained from the memory of the master I/O device.
The problem of configuring and documenting a process control system that uses both remote and local or specialized I/O is further exacerbated by the fact that process controllers and process control systems are usually configured to operate using a different communication strategy than the communication strategy of the remote I/O network. For example, the DeltaV(trademark) controller system manufactured and sold by Fisher-Rosemont Systems, Inc. located in Austin, Tex., has been designed to use a control and communication strategy similar to that used by the Fieldbus protocol. In particular, the DeltaV controller system uses function blocks located in a controller or in different field devices (such as Fieldbus field devices) to perform control operations and specifies interconnections between function blocks using signals given unique signal tags or path names (typically representing where the signals originated) commonly referred to as device signal tags (DSTs). Each function block receives inputs from and/or provides outputs to other function blocks (either within the same device or within different devices), and performs some process control operation, such as measuring or detecting a process parameter, controlling a device or performing a control operation like implementing a proportional-derivative-integral (PID) control routine. The different function blocks within a process control system are configured to communicate with each other (e.g., over a bus or within a controller) to form one or more process control loops, the individual operations of which may be spread throughout the process to make the process control more decentralized. The DeltaV controller uses a design protocol very similar to that used by the Fieldbus devices and, therefore, enables a process control strategy to be designed for the controller and have elements thereof downloaded to the Fieldbus device connected to the controller. Because the DeltaV controller and the Fieldbus devices operate using basically the same function block design construct, the controller can easily communicate with the Fieldbus devices and relate incoming signals from function blocks within the Fieldbus devices to function blocks within the controller. Likewise, Fieldbus devices and other devices that use specialized, local or conventional I/O can and are configured using a common configuration routine because the configuration routine can specify signals to be sent between function blocks, wherein each signal has a unique path or tag name. In fact, because the Fieldbus (which is a specialized I/O environment) and local I/O environments enable communication of each signal from a device separately over a communication channel to the controller, it is a fairly straightforward matter for the controller to send signals to and receive signals from the these devices and to configure the system using these devices using a common configuration database. As a result, the configuration routine for the DeltaV system already provides a combined configuration database having information pertaining to the controller, the Fieldbus field devices and some limited information pertaining to other local or conventional I/O devices such as HART devices already integrated therein. However, because remote I/O device communication protocols, such as the Profibus protocol and the AS-Interface protocol, communicate a string of data related to multiple signals from a device, and cannot communicate signals individually to the controller, use of the configuration systems designed to provide control of local or specialized I/O devices was limited to local or specialized I/O device networks and was not extended to remote I/O device networks.
A process control configuration system integrates the configuration and documentation of devices connected to a control network using local I/O protocols, such as 4-20 ma, and HART protocols or specialized protocols, such as the Fieldbus protocol, with the configuration and documentation of devices connected to the control system using a remote I/O protocol, such as the Profibus and the AS-Interface communication protocols, to thereby enable the control system to communicate with and control different types of field devices using different communication protocols based on a common configuration database. In particular, a process control configuration system enables a user to enter data pertaining to one or more remote I/O devices and, preferably, automatically prompts the user for information pertaining to each of the remote I/O devices connected to the system via a remote I/O network to create device definitions for the remote I/O devices. The remote I/O device information, which may include information pertaining to the signals associated with each of the remote I/O devices, including user assigned signal tags or path names, is stored in the same database as information pertaining to other devices within the process control system, including devices which are connected to the system using local or specialized I/O. If desired, this database may be an object-oriented database having a hierarchy of objects used to define devices, modules and signals associated with devices.
After entering the information pertaining to each of the devices, modules, signals, etc. associated with the remote I/O devices (as well as other devices), the configuration system then creates and downloads to the master I/O master device associated with the remote I/O device network a runtime configuration which enables communication between a controller within the process control system and the remote I/O field devices. This runtime configuration will enable the controller to recognize where each of the signals associated with each of the remote I/O field devices is stored within the master I/O device, what each of those signals represents, the nature of these signals (i.e., whether they are digital, analog, floating point values, integer values, etc.), the signal name or path name associated with the signals, etc. so that the controller has all of the information needed to assign a signal path or signal tag to each of the signals delivered across the remote I/O bus, even though these signals cannot be individually sent across the remote I/O bus.
Still further, the configuration system automatically integrates the documentation of remote I/O devices with local or specialized I/O devices because it uses the same database to store information pertaining to the all of the devices connected to the system, whether they are connected via a local I/O device, a specialized I/O device or a remote I/O device. This documentation may be displayed on a common configuration documentation schematic have information pertaining to the devices in the local, specialized and remote I/O device networks.
According to one aspect of the invention, a configuration system for use in a process control network having a controller, a first device network that communicates using a first input/output protocol (such as a Fieldbus or a HART device network protocol) and a second device network that communicates using a Profibus input/output communication protocol includes a configuration database that stores configuration information pertaining to the first device network and configuration information pertaining to the Profibus device network. A data access routine automatically requests first device network configuration information pertaining to the first device network and second device network configuration information pertaining to the Profibus device network and may create device definitions for the Profibus device network. A configurator then configures the Profibus device network based on the Profibus device network configuration information and stores the Profibus device network configuration information in the configuration database.
According to another aspect of the invention, a method of configuring a process control system including a controller, a first device network that uses a first communication protocol and a Profibus device network which has a Profibus device connected to a Profibus I/O card includes the steps of creating a device definition associated with the Profibus device for storage in a configuration database and using a configuration documentation system to associate an indication of the Profibus device with a port of a Profibus I/O card to reflect the actual connection of the Profibus device to the process control system. The method also includes the steps of assigning a signal tag for a signal associated with the Profibus device, downloading a configuration of the port of the Profibus I/O card to the Profibus I/O card and configuring a control application to be run in the controller using the signal tag.